1. Field of the Invention
The present invention relates to a process for emulsion polymerization and, more particularly, to a process for polymerization wherein, in the emulsion polymerization of vinyl monomer, the polymer is prevented from being deposited on the reactor and the amount of coagulated polymer floating in the latex is reduced.
2. Description of the Prior Art
The aqueous emulsion polymerization of vinyl monomers has been widely adopted industrially in such application fields as synthetic rubbers, plastics and paints because, with emulsion polymerization, it is easy to remove reaction heat and the polymerization reaction is freely controlled.
The emulsifying agents heretofore employed in emulsion polymerization are many, and include salts of higher fatty acids, aliphatic long chain sulfonates, aliphatic long chain sulfuric acid ester salts, alkylarylsulfonates, dialkylsulfosuccinates and alkylpolyoxyalkylene phosphoric acid ester salts.
However, one of the most serious problems in carrying out the emulsion polymerization on an industrial scale by using such emulsifiers is the deposition of the polymer on the inner wall of the reactor and such projecting parts as agitators and thermometers.
Particularly, the deposition of the polymer on the inner wall of the reactor will reduce the thermal conductivity so much that the polymerization heat cannot be removed; the smooth polymerization reaction will be impeded and large amounts of labor and time will be required to remove the deposited polymer and has presented a great problem.
Various measures of preventing such deposition of the polymer on the reactor wall or the like have been investigated. For example, there has been suggested a method wherein the inner surface of the reactor is lined with glass. However, in the method wherein the inner surface of the reactor is lined with glass, although the inner surface of the reactor is smooth and the deposition of the polymer is somewhat less than in conventional reactors made of stainless steel, there have been defects in that the reactor is high in manufacturing cost and is liable to be broken at the time of the operation of the reactor or the cleaning of it to remove the deposited polymer or the like.
As a result of making various investigations in view of this background, the present inventors have completed the present invention by discovering a process wherein these problems can be solved at once by using a special aqueous dispersion medium.